[LLVMdev] #APP/#NOAPP

[reed kotler]

On 05/15/2013 10:53 PM, Richard Smith wrote:
> On Mon, May 6, 2013 at 9:09 AM, reed kotler <rkotler at mips.com 
> <mailto:rkotler at mips.com>> wrote:
>
>     On 05/06/2013 08:51 AM, Rafael Espíndola wrote:
>
>             It's working fine just that it's ugly to see those
>             APP/NOAPP markers.
>
>         Inline assembly is inline assembly. It has the semantics
>         defined in
>         the IL documentation and should all be treated uniformly.
>
>         I guess I would be OK with unconditionally removing those
>         comments (I
>         don't see a lot of value in them) or having different
>         verbosity levels
>         for the asm output.
>
>         What we should never have is a "if (this asm was created by
>         llvm itself)".
>
>     I would like to see a method in asm printer which turns on/off
>     these comments.
>     It's trivial to add and use but I can't put back to this code
>     without permission so there is no point to write the patch if
>     nobody will approve it.
>
>     Then I could call that method when I'm processing  compiler
>     generated stubs that have inline
>     assembly.
>
>     Traditionally these comments are used in gcc so that when you look
>     at assembly code, you can tell which was generated by the compiler
>     and which was inline assembly the user created.
>
>
> This does not appear to be the case. As far as I can discern from the 
> available documentation, #APP and #NOAPP are pragmas which inform the 
> assembler's preprocessor whether it's in "application mode" (where it 
> needs more expensive tokenization rules, including comment-stripping 
> and the like) or whether it's in "processing compiler output mode" 
> (where it can skip all that stuff).
>
> That these pragmas *also* mark where the user's inline asm ended up 
> seems to just be a happy coincidence.

I've read that too in the docs but I don't think it has any meaning here 
because I'm emitting the same kind of code that gcc emits; so I should 
not need them. Possible it slows down compilation by some
tiny amount here.

It does not hurt for me to have the APP/NO_APP markers; I just don't 
like to see them in the .s file.
As Jim Grosbach and others have noted, if I move the inline asm 
generation to another place, I won't get those. It's just because the 
compiler is doing what I user would do that I'm getting them.



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